Modern farming methods employ such devices as bale rollers which roll a swath or windrow of hay or other long fiber forage crops into hugh rolls which are left in the field, or straw bunchers which take the straw from a combine and drop it in large bunches about a field. The prior art contains a number of specialized transport devices which have a normally horizontal bed that may be tilted rearwardly in order that a tractor may back the transport device under a large bale or under a bunch of straw, after which the bed is returned to its horizontal transport position so the hay or straw may be moved to a place of storage. Commonly, such transport devices are provided with conveyor chains that extend the whole length of the bed and that may be driven to push the load off the rear of the bed. In some cases, the chains carry a movable upright wall which bears against the front of the bale or bunch. In other cases they have upstanding hay engaging fingers at intervals along the chains so that by using a reversible drive the conveyors may assist in loading the transport device as well as in unloading it.
Typical of such prior art devices are those disclosed in U.S. Pat. Nos. 2,761,577; 3,366,257; 3,415,400; 3,209,932; and 3,624,786.
A difficulty with all such devices is that they may be loaded only by backing the tractor which requires considerable skill to drive the transport device directly beneath the load in a straight line and which also requires that the tractor operator guess when the entire load is on the transport device or else dismount from the tractor to go to the rear of the transport device.